issue 2632 slice 4: product-docs assemblers operator help (HTML-first/Markdown/Velocity) #4433

Parent

Parent: #2632
Grandparent: #2626

Phase 5 engineering docs already shipped (#2833 implementer guide, #2834 XSL cookbook, #2835 shim criteria). Remaining: operator-facing product-docs (HARD GATE — docs/ai-generated/** is not the product help site).

Slice goal

One user-visible increment: Operators and designers can follow product-docs 8.2 to choose HTML-first, Markdown, or Velocity assemblers on Design / Developer Templates, including when to prefer them over Legacy/XSL.

HARD BAN: do not split REST vs SPA vs Playwright. This slice is product-docs (+ links from existing Design/Templates pages). Do not stack with #4430 pipelines work (hot-path rest.md / Developer Pipelines / WebUI).

In scope

1. Update or extend product-docs/8.2/admin/design-templates.md (and/or a new 8.2 admin/developer page with stable id:) so assembler choices, defaults, and operator steps match shipped 8.2 behavior.
2. Cross-link from getting-started / admin Design / developer templates indexes only if required for nav; prefer in-page links from existing Design templates page to avoid admin/index.md thrash if a pipelines PR is open.
3. Do not delete PSLegacyDefinitionXmlShim (that is Phase 5 residual: remove definition-XML dual-run shim when criteria met #2852, still blocked).
4. scripts/ci-smoke-product-docs.sh (or .bat) green.

Out of scope

• XSL migration cookbook in product-docs (slice 5)
• Dual-run / customer XML upgrade operator path (slice 6)
• Shim deletion (Phase 5 residual: remove definition-XML dual-run shim when criteria met #2852)
• Developer Pipelines / pipeline result pages (issue 1690 slice 3: Pipelines Slice D raw JSON/XML with no presentation #4430)

Acceptance

• Product-docs 8.2 describes HTML-first / Markdown / Velocity assembler operator path accurately
• Stable frontmatter id; existing id: links not broken
• Docs smoke green; comment on [8.2] Template/assembler Phase 5: deprecation cleanup and help #2632 / [8.2] Template & assembler model normalization (epic) #2626 Agent progress
• No pipeline hot-path files (product-docs/8.2/developer/rest.md Pipelines section, admin/developer-pipelines.md, WebUI, sitemanage-beans.xml, perc-qa-automation package.json) unless this is the only open product PR

Modules

product-docs/8.2/

Leave unassigned. Do not add In Progress.

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